A nearby analog of z ∼ 2 compact quiescent galaxies with a rotating disk.
JIANG F., VAN DOKKUM P., BEZANSON R. and FRANX M.
Abstract (from CDS):
Recent studies have identified a population of compact quiescent galaxies at z ∼ 2. These galaxies are very rare today and establishing the existence of a nearby analog could allow us to study its structure in greater detail than is possible at high redshift. Here we present such a local analog, NGC 5845, which has a dynamical mass of Mdyn= 4.3±0.6x1010 M☉and an effective radius of only re= 0.45±0.05 kpc. We study the structure and kinematics with HST/WFPC2 data and previously published spatially resolved kinematics. We find that NGC 5845 is similar to compact quiescent galaxies at z ∼ 2 in terms of size versus dynamical mass (re-Mdyn), effective velocity dispersion versus size (σe-re), and effective velocity dispersion versus dynamical mass (σe-Mdyn). The galaxy has a prominent rotating disk evident in both the photometry and the kinematics: it extends to well beyond ≳ 1/3 effective radius and contribute to ≳ 1/4 of the total light of the galaxy. Our results lend support to the idea that a fraction of z ∼ 2 compact galaxies have prominent disks and positive mass-to-light ratio gradients, although we caution that NGC 5845 may have had a different formation history than the more massive compact quiescent galaxies at z ∼ 2.